of Botany,Chinese Academy Of Sciences
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Carbon versus nitrogen release from root and leaf litter is modulated by litter position and plant functional type
Litters of leaves and roots of different qualities occur naturally above- and below-ground, respectively, where they decompose in contrasting abiotic and biotic environments. Therefore, ecosystem carbon (C) and nitrogen (N) dynamics can be strongly affected by the combination of litter position and quality. However, it is poorly understood how C versus N turnover of litters depend on the interplay among plant functional type (PFT), organs, traits and litter position. In a semi-arid inland dune, soil surface and buried leaf litters and buried fine roots of 25 species across three PFTs (herbs, legume shrubs and nonlegume shrubs) were incubated for 3, 6, 9, 12, 18 and 24 months to investigate litter decomposition and C and N dynamics. Morphological and chemical (nutrient and NMR carbon) traits of initial litters of leaves and fine roots were determined. The litter decomposition rates (k values) of surface leaves and buried fine roots did not differ, but buried fine roots and buried leaf litter decomposed faster than surface leaf litter. Ratios of k values of surface leaves to buried leaves decreased with leaf C:N ratio. Herbs and legume shrubs decomposed faster than nonlegume shrubs for buried fine roots, but not for leaves. At given C loss, buried fine roots had higher N loss than leaf litters; legume shrubs with relatively higher N or lower C:N ratio had higher N loss than nonlegume shrubs. Stronger positive relationships between C and N losses were shown in leaves and legume shrubs than in fine roots and nonlegume shrubs respectively. Synthesis. The generality of faster N release of legume litters at given C release highlights the importance of legumes in N cycling in semi-arid ecosystems where N is the limiting factor. The dynamics and coordination of C versus N release as a function of litter quality are modulated by litter position and PFT. These findings have important implications for the development of process-based models on C and N cycles in the context of on-going global change potentially altering the functional composition of plant communities and the relative quantities and qualities of above-ground versus below-ground litter
Precipitation consistently promotes, but temperature inversely drives, biomass production in temperate vs. alpine grasslands
Comparisons of vegetation production between temperate and alpine grasslands are not well studied, and the understanding of the underlying mechanisms is still incomplete. To address this issue, we selected the Inner Mongolia and Tibet regions to conduct large-transect surveys for temperate grassland (TG) and alpine grassland (AG), respectively, in China, to reveal the universal and differential mechanisms of above-and belowground biomass production (GB, AGB and BGB) and precipitation use efficiencies (PUE) in the two grasslands. The relative importance of climatic factors on biomass and PUE is greater than that of soil and biological factors. Elevated mean annual precipitation (MAP) consistently increased GB in both TG and AG. Increased mean annual temperature (MAT) reduced GB by weakening the soil nutrient status in TG, whereas it increased GB by improving the soil nutrient status in AG. MAP promoted more AGB than BGB in TG, whereas MAT affected BGB more than AGB in AG. When the multicomponent heterogeneity of other factors in grasslands was eliminated, the effect of MAP on GB remained significant for both TG and AG. After removing the effect of multifactorial het-erogeneity, however, the significant effect of MAP on PUE of the two grasslands was largely enhanced. From these results, we can conclude that climatic factors do not always exert identical effects on different grasslands. In particular, highlighting the divergent mechanisms of biomass production and precipitation use efficiency between temperate and alpine grasslands can improve the understanding of the carbon sink and hydraulic sensitivity of various grasslands
Insights into the evolutionary history and taxonomic status of Sinopteris (Pteridaceae)
As an endemic Chinese genus, Sinopteris C. Chr. & Ching was once considered an early diverged taxon of chei-lanthoid ferns, and its taxonomic status has long been controversial. In this study, eight datasets spanning the complete chloroplast genomes and three nuclear genes were used to reconstruct the phylogeny of Sinopteris and its relatives. In addition, combining morphological analyses, divergence time estimation, and ancestral trait reconstruction, the origin and evolutionary history of Sinopteris were comprehensively discussed. Based on the complete chloroplast genome dataset, our analyses yielded a phylogram with all clades strongly supported (ML -BS = 100, BI-PP = 1.0), and the topology was almost identical to that based on the concatenated sequences of nrDNA, CRY2, and IBR3. Two species of Sinopteris were united and sister to Aleuritopteris niphobola (C. Chr.) Ching. They constituted a stable monophyletic group embedded in Aleuritopteris Fe ' e. This was also consistent with the results of morphological analyses. Divergence time estimation indicated that the clade of Aleuritopteris and Sinopteris originated in the early Miocene (ca. 16.80 Ma) and experienced two rapid diversifications, which could coincide with environmental heterogeneity caused by the progressive uplift of the Himalayas and the intense uplift of the Hengduan Mountains. Sinopteris originated in the late Miocene (ca. 6.96 Ma), accompanied by the sharp intensifications of Asian Monsoon, and began to diversify at 2.34 Ma, following the intense uplift of the Hengduan Mountains. Ancestral character reconstruction showed that monangial sori and subsessile sporangia were clearly late derived states rather than early diverged states. Both the molecular phylogenetic and morphological analyses support the inclusion of Sinopteris in Aleuritopteris
Reorganization of three-dimensional chromatin architecture in Medicago truncatula under phosphorus deficiency
Emerging evidence reveals that the three-dimensional (3D) chromatin architecture plays a key regulatory role in various biological processes of plants. However, information on the 3D chromatin architecture of the legume model plant Medicago truncatula and its potential roles in the regulation of response to mineral nutrient deficiency are very limited. Using high-resolution chromosome conformation capture sequencing, we identified the 3D genome structure of M. truncatula in terms of A/B compartments, topologically associated domains (TADs) and chromatin loops. The gene density, expressional level, and active histone modification were higher in A compartments than in B compartments. Moreover, we analysed the 3D chromatin architecture reorganization in response to phosphorus (P) deficiency. The intra-chromosomal cis-interaction proportion was increased by P deficiency, and a total of 748 A/B compartment switch regions were detected. In these regions, density changes in H3K4me3 and H3K27ac modifications were associated with expression of P deficiency-responsive genes involved in root system architecture and hormonal responses. Furthermore, these genes enhanced P uptake and mobilization by increasing root surface area and strengthening signal transduction under P deficiency. These findings advance our understanding of the potential roles of 3D chromatin architecture in responses of plants in general, and in particular in M. truncatula, to P deficiency. Reorganization of the 3D chromatin architecture is associated with transcriptional regulation to enhance phosphorus uptake and mobilization in Medicago truncatulaunder phosphorus deficiency
Identifying thresholds of nitrogen enrichment for substantial shifts in arbuscular mycorrhizal fungal community metrics in a temperate grassland of northern China
Nitrogen (N) enrichment poses threats to biodiversity and ecosystem stability, while arbuscular mycorrhizal (AM) fungi play important roles in ecosystem stability and functioning. However, the ecological impacts, especially thresholds of N enrichment potentially causing AM fungal community shifts have not been adequately characterized. Based on a long-term field experiment with nine N addition levels ranging from 0 to 50 g N m(-2) yr(-1) in a temperate grassland, we characterized the community response patterns of AM fungi to N enrichment. Arbuscular mycorrhizal fungal biomass continuously decreased with increasing N addition levels. However, AM fungal diversity did not significantly change below 20 g N m(-2) yr(-1), but dramatically decreased at higher N levels, which drove the AM fungal community to a potentially unstable state. Structural equation modeling showed that the decline in AM fungal biomass could be well explained by soil acidification, whereas key driving factors for AM fungal diversity shifted from soil nitrogen : phosphorus (N : P) ratio to soil pH with increasing N levels. Different aspects of AM fungal communities (biomass, diversity and community composition) respond differently to increasing N addition levels. Thresholds for substantial community shifts in response to N enrichment in this grassland ecosystem are identified
A juvenile skull from the early Palaeocene of China extends the appearance of crocodyloids in Asia back by 15-20 million years
The earliest Crocodylia from Asia have been represented so far only by alligatoroids and planocraniids. Although definitive crocodyloids are not known until the late Eocene, it has been hypothesized that Asiatosuchus-like basal crocodyloids originated in Asia before the late Palaeocene. In this paper, we describe a new fossil crocodyloid from the lower Palaeocene of Qianshan Basin, Anhui Province, China. The skull and lower jaw fragment exhibit several characteristics typical of juvenile crocodylians. They also display a combination of features not seen in any other taxon, warranting the erection of a new species and genus, Qianshanosuchus youngi gen. & sp. nov. Its affinities are tested in phylogenetic analyses based on two recent character matrices of Eusuchia. To assess the effect of juvenile characteristics on the outcome of the phylogenetic analyses, juvenile specimens of extant crocodylian taxa are analysed in the same way, showing that the effect of their ontogenetic stage on their placement in the tree is minimal. Our analyses point to a basal crocodyloid position for Q. youngi. With these findings, the presence of Crocodyloidea in Asia is extended to the early Palaeocene, 15-20 Myr earlier than formerly thought. Furthermore, our results corroborate previous hypotheses of a Palaeocene dispersal route of Asiatosuchus-like crocodyloids from Asia into Europe
Cytosolic disproportionating enzyme2 is essential for pollen germination and pollen tube elongation in rice
Cytosolic DISPROPORTIONATING ENZYME2 converts maltose to glucose, providing energy and cellular materials for pollen germination and pollen tube elongation in rice. Degradation of starch accumulated in pollen provides energy and cellular materials for pollen germination and pollen tube elongation. Little is known about the function of cytosolic disproportionating enzyme2 (DPE2) in rice (Oryza sativa). Here, we obtained several DPE2 knockout mutant (dpe2) lines via genomic editing and found that the mutants grew and developed normally but with greatly reduced seed-setting rates. Reciprocal crosses between dpe2 and wild-type plants demonstrated that the mutant was male sterile. In vitro and in vivo examinations revealed that the pollen of the dpe2 mutant developed and matured normally but was defective in germination and elongation. DPE2 deficiency increased maltose content in pollen, whereas it reduced the levels of starch, glucose, fructose, and adenosine triphosphate (ATP). Exogenous supply of glucose or ATP to the germination medium partially rescued the pollen germination defects of dpe2. The expression of cytosolic phosphorylase2 (Pho2) increased significantly in dpe2 pollen. Knockout of Pho2 resulted in a semi-sterile phenotype. We failed to obtain homozygous dpe2 pho2 double mutant lines. Our results demonstrate that maltose catalyzed by DPE2 to glucose is the main energy source for pollen germination and pollen tube elongation, while Pho2 might partially compensate for deficiency of DPE2
Impacts of methyl jasmonate on Selaginella martensii: volatiles, transcriptomics, phytohormones, and gas exchange
Exposing Selaginella martensiito methyl jasmonate caused profound transcriptomic changes, dose-dependent increases in stress volatile emissions, increased 12-oxo-phytodienoic and jasmonic acid concentrations, and decreased gas exchange rate. Methyl jasmonate (MeJA) induces various defence responses in seed plants, but for early plant lineages, information on the potential of jasmonates to elicit stress signalling and trigger physiological modifications is limited. The spikemoss Selaginella martensii was exposed to a range of MeJA concentrations (0, 10, 25, and 50 mM), and biogenic volatile organic compound (BVOC) emissions, photosynthetic rate (A), and stomatal conductance (g(s)) were continuously measured. In addition, changes in phytohormone concentrations and gene expression were studied. Enhancement of methanol, lipoxygenase pathway volatiles and linalool emissions, and reductions in A and g(s), were MeJA dose-dependent. Before MeJA treatment, the concentration of 12-oxo-phytodienoic acid (OPDA) was 7-fold higher than jasmonic acid (JA). MeJA treatment rapidly increased OPDA and JA concentrations (within 30 min), with the latter more responsive. Some genes involved in BVOC biosynthesis and OPDA-specific response were up-regulated at 30 min after MeJA spraying, whereas those in the JA signalling pathway were not affected. Although JA was synthesized in S. martensii, OPDA was prioritized as a signalling molecule upon MeJA application. MeJA inhibited primary and enhanced secondary metabolism; we propose that fast-emitted linalool could serve as a marker of elicitation of stress-induced metabolism in lycophytes
High-precision early warning system for rice cadmium accumulation risk assessment
Rapid global industrialization has resulted in widespread cadmium contamination in agricultural soils and products. A considerable proportion of rice consumers are exposed to Cd levels above the provisional safe intake limit, raising widespread environmental concerns on risk management. Therefore, a generalized approach is urgently needed to enable correct evaluation and early warning of cadmium contaminants in rice products. Combining big data and computer science together, this study developed a system named SMART Cd Early Warning, which integrated 4 modules including genotype-to-phenotype (G2P) modelling, high-throughput sequencing, G2P prediction and rice Cd contamination risk assessment, for rice cadmium accumulation early warning. This system can rapidly assess the risk of rice cadmium accumulation by genotyping leaves at seeding stage. The parameters including statistical methods, population size, training population-testing population ratio, SNP density were assessed to ensure G2P model exhibited superior performance in terms of prediction precision (up to 0.76 +/- 0.003) and computing efficiency (within 2 h). In field trials of cadmium-contaminated farmlands in Wenling and Fuyang city, Zhejiang Province, SMART Cd Early Warning exhibited superior capability for identification risk rice varieties, suggesting a potential of SMART Cd Early-Warning system in OsGCd risk assessment and early warning in the age of smart
Classification of rose petal colors based on optical spectrum and pigment content analyses
Roses (Rosa sp.) are an important ornamental crop worldwide. Their colorful flowers mainly reflect an accumulation of anthocyanins and carotenoids. Developing a reliable method to classify rose petal color and identifying relationships between pigment contents and color space values may offer better evaluation criteria for rose varieties. In this study, we classified 60 rose varieties into three groups based on their color parameters, corresponding to red varieties, white and yellow varieties, and pink and dark pink varieties. We measured the total pigment contents and identified the underlying anthocyanins and carotenoids using both UV spectrophotometry and ultraperformance convergence chromatography coupled to mass spectrometry. Flower petals of white roses contained the lowest pigment levels, while those of yellow roses contained only carotenoids (40.65-244.42 mu g/g) and mainly in the form of beta-carotene and violaxanthin. The petals of pink and dark pink roses only accumulated anthocyanins (91.72-1703.93 mu g/g) and mainly as cyanidin 3,5-diglucoside and cyanidin 3-O-glucoside. The petals of red roses contained both large amounts of anthocyanins (1484.8-3806.22 mu g/g) and small amounts of carotenoids (1.81-18.77 mu g/g). We divided the 60 rose varieties tested here into five color groups based on optical spectrum and pigment content analyses. We also explored the relationships between anthocyanin contents, carotenoid contents, and flower color space values using principal component analysis, Pearson's correlations, and non-linear models. In addition to providing a more accurate system of rose petal color classification, our results can be used to predict pigment contents based on color parameters